Stem cell therapy has shown great efficacy in many diseases. However, the treatment mechanism is still unclear, which is a big obstacle for promoting clinical research. Therefore, it is particularly important to track transplanted stem cells in vivo, find out the distribution and condition of the stem cells, and furthermore reveal the treatment mechanism. Many tracking methods have been developed, including magnetic resonance imaging (MRI), fluorescence imaging, and ultrasound imaging (UI). Among them, MRI and UI techniques have been used in clinical. In stem cell tracking, a major drawback of these technologies is that the imaging signal is not strong enough, mainly due to the low cell penetration efficiency of imaging particles. Cell penetrating peptides (CPPs) have been widely used for cargo delivery due to its high efficacy, good safety properties, and wide delivery of various cargoes. However, there are few reports on the application of CPPs in current stem cell tracking methods. In this review, we systematically introduced the mechanism of CPPs into cell membranes and their advantages in stem cell tracking, discussed the clinical applications and limitations of CPPs, and finally we summarized several commonly used CPPs and their specific applications in stem cell tracking. Although it is not an innovation of tracer materials, CPPs as a powerful tool have broad prospects in stem cell tracking.

中文翻译：

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细胞穿透肽在干细胞追踪中的应用前景

干细胞疗法在许多疾病中显示出巨大的疗效。但目前治疗机制尚不明确，是推动临床研究的一大障碍。因此，在体内追踪移植的干细胞，了解干细胞的分布和状况，进而揭示治疗机制就显得尤为重要。已经开发了许多跟踪方法，包括磁共振成像 (MRI)、荧光成像和超声成像 (UI)。其中，MRI和UI技术已应用于临床。在干细胞追踪中，这些技术的一个主要缺点是成像信号不够强，主要是由于成像粒子的细胞穿透效率低。细胞穿透肽（CPPs）因其高效、安全性能好，各种货物运输范围广。然而，目前关于CPPs在干细胞追踪方法中的应用报道很少。在这篇综述中，我们系统地介绍了 CPPs 进入细胞膜的机制及其在干细胞追踪中的优势，讨论了 CPPs 的临床应用和局限性，最后总结了几种常用的 CPPs 及其在干细胞追踪中的具体应用。虽然不是示踪材料的创新，但CPPs作为一种强大的工具在干细胞追踪方面有着广阔的前景。讨论了CPPs的临床应用和局限性，最后总结了几种常用的CPPs及其在干细胞追踪中的具体应用。虽然不是示踪材料的创新，但CPPs作为一种强大的工具在干细胞追踪方面有着广阔的前景。讨论了CPPs的临床应用和局限性，最后总结了几种常用的CPPs及其在干细胞追踪中的具体应用。虽然不是示踪材料的创新，但CPPs作为一种强大的工具在干细胞追踪方面有着广阔的前景。